Method of fabricating and attaching pierce nuts to a panel

ABSTRACT

A strip containing a series of flanged pierce nuts connected by flexible and severable sections for use in automatically applying flanged pierce nuts to a panel. The method of forming the strip is also disclosed and comprises providing a blank strip formed with opposed laterally extending flanges, perforating the strip between the flanges, and then slotting the strip between adjacent perforations to form the nut body, after which the sides of the strips are straightened, the holes are threaded and the strip coiled into predetermined lengths. Further, there is disclosed the method of applying pierce nuts from such strip to a panel.

United States Patent Grube METHOD OF FABRICATING AND ATTACHING PIERCENUTS TO A PANEL [72] Inventor: William L. Grube, Lake Bluff, 111.

[73] Assignee: MacLean-Fogg Lock Nut Co., Mundelein,l1l.

[22] Filed: March 23, 1970 [21] Appl. No.: 21,777

[52] US. Cl. ..29/417, 29/432.2, 29/509, 85/32, 206/56 A, 221/71,151/41172, l5l/41.73

[51] Int. Cl ..B23p 17/00, B23p 11/00 [58] Field of Search.....29/4l7,432.2, 432, 509, 513; s 5/32,32.1; 24/73 PEN/73R; 221/71, 73;

206/56 A, 56 AB; 151/41.72, 11.73; 22 7/86 [56] References Cited UNITEDSTATES PATENTS 1,757,142 6/1930 Renner ..29/417'UX 1,852,978 4/1932Mitchel ..29/417 UX 2,187,647 1/1940 Double et a1 ..29/432 UX 2,652,9429/1953 Muchy ..29/432 UX [151 3,704,507 51 Dec. 5,197;

2,749,606 6/1956 Donahue ..29/432 2,754,516 7/1956 Gasstrom ..2'9/417 X3,152,628 10/1964 Strain et' a1 ..29/432 X 2,604,986 7/1952 Berg..206/56 AB UX 3,007,169 11/1961 La Fleur et a1. ..227/86 3,140,0107/1964 Double ..221/73 3,177,915 4/1965 La Fleur et a1. ..151/41.723,624,867 12/1971 Reynolds ..24/73 PF Primary Examiner-Charlie T. MoonAttorney-Davis, Lucas, Brewer & Brugman [57] ABSTRACT A strip containinga series of flanged pierce nuts connected by flexible and severablesections for use in automatically applying flanged pierce nuts to apanel. The method of forming the strip is also disclosed and comprisesproviding .a blank strip formed with opposed laterally extendingflanges, perforating the strip between the flanges, and then slottingthe strip between adjacent perforations to form the nut body, afterwhich the sides of the strips are straightened, the holes are threadedand the strip coiled into predetermined lengths. Further, there isdisclosed the method of applying pierce nuts from such strip to a panel.

5 Claims, 13 Drawing Figures P'A'TENTED DEE 5 m2 SHEET 3 OF 3 METHOD OFFABRICATING AND ATTACHING PIERCE NUTS TO A PANEL This invention relatesto nuts connected together in strip form and to methods of forming andapplying such nuts to a panel. The invention will be described withreference to its application to pierce nuts, which are nuts used aspunches to form openings for themselves in a panel to which they are tobe rigidly secured.

At present, the use of pierce nuts is limited to extremely high volumeapplications, since the handling, selecting, orienting and feeding ofindividual nuts from a hopper requires a large amount of expensivetooling and set-up. Furthermore, existing systems for handling piercenuts are highly specialized in the sense that the entire system offeeding, selecting and applying the nuts must be custom designed foreach application inasmuch as the form of the panel and the location ofthe pierce nut on the panel vary in each instance.

It is an object of this invention to provide a method of handling piercenuts which eliminates the steps of selecting, orienting and locatingsaid nuts prior to the application of the nuts to a panel.

Another object of this invention is the provision of a plurality ofpierce nuts as a series of connected nuts forming a strip which may becoiled and then fed from such coil to a punch press where they areindividually severed from the coil and applied to a panel.

Yet another object of this invention is to provide a method of formingpierce nuts from a strip of metal as a series of connected nuts, theconnections being flexible to permit coiling the strips after the nutsare formed and severing them at their point of application to a panel.

These and other objects of this invention will become apparent from thefollowing detailed description of preferred embodiments of the novelstrip of connected nuts, the method of forming the strip and the methodof applying the nuts to a panel, all of which are depicted in theaccompanying drawings in which:

FIG. 1 is a schematic diagram of the sequence of steps performed upon astrip of metal to produce a coil of connected pierce nuts;

FIG. 2 is a plan view of the strip showing its progressivetransformation by the steps in the method of this invention;

FIG. 2a is a cross section through the strip in its original form;

FIGS. 3 and 4 are respectively bottom and side views of the strip ofFIG. 2;

FIG. 5 is an enlarged side elevation in section of a fragment .of thestrip of FIG. 2 taken along line 55 of FIG. 2;

FIGS. 6 and 7 are enlarged transverse sections of the strip taken alonglines 6-6 and 7-7 of FIG. 4;

FIGS. 8, 9 and 10 are enlarged fragmentary elevations in sections of amodified form of pierce nut, the Figures showing three sequential stepsin the application of such nut to a panel;

FIG. 11 is a bottom view in perspective showing the steps in applyingthe pierce nut of FIG. 2 to a panel; and

FIG. 12 is a bottom view in perspective showing the steps in applyingthe modified form of pierce nut of FIGS. 8, 9 and 10 to a panel.

The general objectives of this invention are attained by forming nuts ina punch press from strip stock having a predetermined rolled section butinstead of shearing the nuts completely from the strip at the end of theforming operation, the strip is merely perforated between the nuts insuch a manner as to leave a thin web of material between the nuts. Theweb will be durable enough to make it possible for the strip to becoiled into a roll and thereafter shipped and handled as a finishedproduct. The rolls of nuts may thus be sold and transported to customersas correctly oriented and precisely located nuts for use with a toolwhich feeds the nuts from the coil, one at a time to a die for furtherprocessing. The latter may, for example, locate the nut on a panel towhich it is to be attached, sever it from the strip, pierce the panelwith it and clinch the nut to the panel.

The initial rolled section may be purchased from a mill to have theprecise cross sectional profile and metallurgy desired, but it is alsopossible for the nut manufacturer to provide tooling for shaping theinitial rolled section to have the cross section he desires.

Referring now to FIGS. 1 and 2 for a detailed description of theinvention, the material from which the nuts are made is shown as a stripof steel having the desired physical characteristics purchased in coilform from a steel mill which has rolled or otherwise produced apredetermined initial cross section in the strip. The fastener selectedto illustrate this invention is a pierce nut which is flanged on two ofits opposed sides, the flanges acting as abutments when the nut isinstalled on a panel to resist pulling the nut through the panel.Accordingly, as shown in FIG. 2a, the contour of the starting materialis generally rectangular, as shown at 20, with flanges 21 and 22 formedon opposite sides of the rectangular section. The starting material maybe supplied in coil form, and when pulled from its initial coil, thestrip containing the section shown in FIG. 2 may be somewhat bent, asshown at 23 in FIG. I. The first operation, therefore, to be performedon the strip is a straightening operation. This is shown at 24 in FIG.1, the strip straightener comprises a series of staggered rolls 25, 26from which the strip, designated 27, is passed to a pair of feed rolls28.

From the feed rolls, the strip 27 is advanced to a punch press at whichmay be set up a progressive die 29, the first operation in which is aperforating operation. It is contemplated that several nuts will beformed simultaneously and accordingly three cylindrical punches 30 areprovided at this station, said punches creating three spaced round holes31, 32 and 33 in the strip 27. The creation of holes 31, 32 and 33 isaccompanied by a spreading of the material of the strip 27 laterally toform bulges 34, 35 and 36 on both sides of strip 27.

The next operation performed by progressive die 29 is a slottingoperation which not only forms the remaining two sides of the finishednut but removes enough material from between adjacent nuts to leave onlya part of each flange 21, 22 to connect adjacent nuts together. Thus,die 29 is provided with punches 37, 38 and 39 which are of elongaterectangular cross section and form the slots 40, 41 and 42,respectively. It may be noted that said slots extend into the flanges 21and 22 so that the sides 43 and 44 of a nut are completely formed, whileat the same time the flanges 21 and 22 have been reduced in width toform relatively thin but durable connecting sections 45 and 46 betweenadjacent nuts.

The third operation performed by progressive die 29 is a side trimmingoperation designed to remove the bulges 34, 35 and 36 from the nuts. Theside trimming punch is shown at 47 and comprises a simple straightsidedpunch which shaves the material of the bulges off the sides and coins itinto the flanges 21 and 22. This operation finishes off the other twostraight sides 48 and 49 of the nut.

Generally accepted design practice for nuts requires that the holes becountersunk to at least the root diameter of the threads to facilitatestarting the screw or bolt into the nut. A countersinking operation maybe incorporated in the side trimming operation of the progressive die29. The countersinking may be performed as a coining operation by theupper part of the trimming die, pins (not shown) on said upper partentering the perforations to locate the, strip correctly relative to thetrimming die while at the same time forming the countersink. FIG. 5shows the countersink 56 of one hole 33 as an example.

From die 29, the strip is moved into a tapping machine shown at 50 whichmay be designed to tap a plurality of holes simultaneously. Because ofthe lateral space required for each tapping unit, the holes tappedsimultaneously may not be adjacent one another, but the first tap 51will tap the first hole of one plural-hole unit operated on by die 29,the second tap 52 will tap the second hole of the adjacent plural-holeunit, and the third tap 53 will tap the third hole of the third adjacentplural-hole unit.

From the tapper 50 the strip 27 is coiled upon a suitable mandrel (notshown) to form a coil 54 containing a predetermined number of nuts. Thecoil is then severed from the strip by a cut-off die 55 and is ready forshipment to a customer who will apply the nuts individually to a panelin a suitable manner and with the aid of suitable tools and dies.

During the coiling process, the strip is bent at the connecting sections45 and 46 so that the nut portion bounded by the sides 43, 44, 48 and 49is not in any manner distorted to impair its usefulness as a fastener.

FIGS. 5, 6 and 7 show sections through the strip 27 after the holes havebeen tapped and the strip is ready for coiling. Each of the holes hasthreads 57 cut thereinto, so that the nut is complete with the sideflanges 21 and 22 required for pierce nuts, and the connecting sectionsbetween nuts, as shown in FIG. 7, are reduced to only that cross sectionwhich is determined to be necessary to permit handling the nuts as astrip. Obviously, the amount of material left in the: sections 45 can bevaried by appropriately lengthening or shortening the punches 37, 38 and39 to remove more or less of the flanges 21 and 22.

Referring now to FIG. 11, the manner in which the nuts are applied to apanel 58 will now be described. Said nuts are moved to the left, asviewed in FIG. 11, in the strip form into an appropriate die whichsevers a nut 59 from the strip at a line shown dotted at 60 and which ismerely an extension of the transverse wall 59 of the nut. In the sameoperation, the connecting segment 45 may also be removed to leave aclean wall 60 on the opposite side of said nut. Where the nut will beconcealed in the final installation of the panel to which it isattached, the connecting segment may be left on the nut since it in noway hinders the piercing or clinching operation to be performed on thenut. The severed nut is then operated upon by a suitable punch such asthat shown at 67 in FIG. 8 and advanced by said punch through the panel58 and upon an appropriate die. Said die causes nut 59 to pierce panel58 and remove therefrom a substantially rectangular slug 61 while at thesame time forming in the corners of the protruding nut, shaved or upsetmetal 62, as shown in FIG. 11, which bears against the bottom surface ofpanel 58 to clinch nut 59 to said panel. It is understood that suitablelocating means will be provided (not shown) for the nut 59 on panel 58.

Although this invention has been described with reference to clinch nutswhich have flat sides parallel to the axis of the nut for use with thepiercing and clinching method disclosed in my aforesaid copendingapplication, the method is also applicable with modifications to piercenuts which depend upon an inwardly directed movement of the panelmaterial toward the sides of the nut for a clinching action.

One such modification is shown in FIGS. 8, 9 and 10 from which it may beobserved that the nut is of substantially the same size and proportionand made from substantially the same strip of metal as the nut of FIGS.2-7, except that the sides adjacent the flanges 63, 64 have beenundercut, as shown at 65 and 66 in FIG. 8. In that figure, a suitablepunch 67 and die 68 are used, the latter being adapted to move thematerial of the panel 69 inwardly into the undercut 6S and 66 to clinchthe nut to the panel 69. Thus, die 68 has a tapered bead 70 formed oneach side of an opening 71 therein upon which panel 69 initially rests.

The first stage in the operation of the die of FIG. 8 is shown in FIG. 9and comprises displacing a slug 72 from the central regions of the die68. The final operation is shown in FIG. 10 and comprises displacingmaterial 73 and 74 from the sides of the opening 75 (FIG. 9) in thepanel 69 inwardly of the nut into the undercuts 65 and 66.

FIG. 12 shows a nut 76 on the end of a strip formed with undercut sidesas it is applied to a panel 77 in accordance with the dies shown inFIGS. 8, 9 and 10. It may be apparent that the method of forming a strip78 of connected undercut nuts 76 is substantially identical with thatdisclosed in connection with the straightsided nuts of FIG. 2, exceptthat the punch 47 is omitted and special grinders (not shown) or othersurface shaping tools are substituted for punch 47 to remove the bulgesformed in the perforating operation.

It may thus be observed that by forming pierce nuts as readily severableparts of a strip, the usual nut orienting, selecting and feedingoperations are completely eliminated and the handling of the nuts can beeffected without the use of containers. Furthermore, in the applicationof the nuts to a panel from a strip, it is possible in one stroke of apress to sever a nut from a strip, pierce a panel with the nut andclinch the nut to the panel.

I claim:

1. The method of fabricating and attaching pierce nuts to a panelcomprising the steps of providing a relatively inflexible continuousmetal blank for forming a plurality of spaced nut bodies, said blankhaving a thickness of substantially that of the finished pierce nuts,forming a rigid abutment extending laterally of the blank and of alesser thickness than the nut body, punching material out of the thickerportion of the blank to form a relatively flexible metallic connectorbetween spaced nut bodies of less cross-sectional area than thecross-sectional area of the abutment, piercing and tapping the nutbodies to form a strip of substantially completely shaped spaced piercenuts joined together by said relatively flexible metallic connectors,feeding an end nut of said strip under a plunger, severing said end nutof said strip from said strip with said plunger, piercing a panel withsaid nut body, pushing said nut body through the pierced panel until theabutment is adjacent to said panel, and clinching the nut body to thepanel on the side thereof opposite the abutment.

2. The method according to claim 1, said severing, piercing, pushing andclinching steps being performed with a single stroke of a plunger.

3. The method according to claim 1, comprising the further steps offorming the abutment as a laterally extending first flange on said nutbody, forming a second laterally extending flange on the opposite sideof the nut body from said first flange, said nut bodies and flangesforming a single metallic strip.

4. The method of attaching pierce nuts to a panel as defined in claim 1,and wherein the securement of the nut in its mounted position on thepanel is effected by a die and comprises the deformation of the paneladjacent the mounted nut.

5. The method of attaching pierce nuts to a panel as defined in claim 1,and wherein the securement of the nut in its mounted position on thepanel is effected by a die and comprises the deformation of segments ofthe nut into clamping engagement with the panel.

1. The method of fabricating and attaching pierce nuts to a panel comprising the steps of providing a relatively inflexible continuous metal blank for forming a plurality of spaced nut bodies, said blank having a thickness of substantially that of the finished pierce nuts, forming a rigid abutment extending laterally of the blank and of a lesser thickness than the nut body, punching material out of the thicker portion of the blank to form a relatively flexible metallic connector between spaced nut bodies of less cross-sectional area than the cross-sectional area of the abutment, piercing and tapping the nut bodies to form a strip of substantially completely shaped spaced pierce nuts joined together by said relatively flexible metallic connectors, feeding an end nut of said strip under a plunger, severing said end nut of said strip from said strip with said plunger, piercing a panel with said nut body, pushing said nut body through the pierced panel until the abutment is adjacent to said panel, and clinching the nut body to the panel on the side thereof opposite the abutment.
 2. The method according to claim 1, said severing, piercing, pushing and clinching steps being performed with a single stroke of a plunger.
 3. The method accoRding to claim 1, comprising the further steps of forming the abutment as a laterally extending first flange on said nut body, forming a second laterally extending flange on the opposite side of the nut body from said first flange, said nut bodies and flanges forming a single metallic strip.
 4. The method of attaching pierce nuts to a panel as defined in claim 1, and wherein the securement of the nut in its mounted position on the panel is effected by a die and comprises the deformation of the panel adjacent the mounted nut.
 5. The method of attaching pierce nuts to a panel as defined in claim 1, and wherein the securement of the nut in its mounted position on the panel is effected by a die and comprises the deformation of segments of the nut into clamping engagement with the panel. 